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"You've never read anything like this," says one reviewer optimistically in the publishing blurb for the latest in a long line of a books, investigations and even films about the Zodiac Killer - arguably the most puzzling murder investigation in US history.

The series of killings, which have never been solved, have fascinated the United States since the late 1960s when the killer - so-called because of the cryptic clues and coded letters he sent to local newspapers - killed at least five people, perhaps more, in the San Francisco area.

Today, another theory about the identity of the killer emerged. New York magazine reported that a new book being published by HarperCollins, called the The Most Dangerous Animal of All, would allege the book's author, Gary L Stewart, had discovered that his father was the Zodiac Killer.

Police say the crimes remain "unsolved" with the only credible suspect, Arthur Leigh Allen, having been cleared by DNA evidence before his death in 1992.

New York magazine reported that "for months" staff at HarperCollins in New York kept the existence of the "explosive new book" quiet. It describes Mr Stewart's 10-year search for his biological father, leading to a chilling discovery. "His father is one of the most notorious and still at large serial killers in America. It was a quest that would lead him to a horrifying truth and force him to reconsider everything he thought he knew about himself and his world." the publishers state.

Written with award-winning author and journalist Susan D Mustafa the book is said to have finally unmasked the serial killer.

Tina Andreadis at HarperCollins told the New York magazine: "If you look at Gary's photo next to the sketch of the Zodiac, next to his father's mug shot, you can see that there is very clearly more than just a passing resemblance."

She added that Mr Stewart had not wanted to believe his estranged father was a murderer. According to Ms Andreadis, the book was vetted by HarperCollins lawyers who felt it was "legally sound".

The development will open yet another chapter in a case that has fascinated Hollywood for decades, providing the loose inspiration for the Clint Eastwood hit Dirty Harry and the 2007 thriller Zodiac, among others. The Zodiac killer first struck in 1968, when he shot high-school students Betty Lou Jensen and David Faraday in a "lovers' lane" in the city of Benicia. He was blamed for a string of further attacks.

According to the Los Angeles Times, some 1,200 people have claimed to know the identity of the true killer. However, many are viewing the latest theory with scepticism.